OnePlus has announced that for the first time it will sell one of its smartphones without the need for an invite on a permanent basis, as it marks its second birthday and a maturing in the way the company operates.

The OnePlus 2, the company's smartphone billed as a "2016 flagship killer," was launched in August and, like the company's first ever smartphone, was only available to those with an invite, limiting consumers' ability to buy them. While the company has previously held flash sales -- such as one on Black Friday -- where the phones have been temporarily available without an invite, from midnight on Dec. 5, the company will make the OnePlus 2 invite-free forever.

The decision comes just two weeks before the company will celebrate its second birthday on Dec. 17 and to mark the occasion, company co-founder Carl Pei says it is time for the company to take more of a risk. "We are always trying to enhance the OnePlus experience for [customers] and taking risks to push ourselves and show real improvements," Pei said, in a blog post. "That's why we're making the OnePlus 2 invite-free forever."

The company's other smartphone, the budget-friendly OnePlus X, will however remain on sale through the invite system, though there will be weekly open sales for the smartphone and over the Dec.5-7 weekend it will be available invite-free. OnePlus has not revealed any details of sales figures for either of its 2015 smartphones.

OnePlus X Review The OnePlus X costs just $249 and is considered by many to be the best-value smartphone on the market. Photo: David Gilbert

The China-based smartphone brand OnePlus has garnered a disproportionately high amount of media attention given its modest sales figures. This is down to a combination of promising smartphones with a "flagship" experience at a budget price as well as the innovative sales system that meant only those with an invite could purchase one of the phones.

The system worked insomuch as it helped catapult OnePlus into the consciousness of smartphone buyers the world over without spending huge gobs of cash on marketing. However it also frustrated users who wanted to buy the company's smartphones but simply couldn't get access to one.

While the invite system has worked in the company's favor in relation to attracting media attention, there has also been a more practical reason for the system. OnePlus has been attempting to keep its operation as lean as possible and part of that has been stopping the build-up of a lot of stock, which for a fledgling operation like OnePlus can cripple cash flow and if sales don't go as expected could prove fatal.

As co-founder Pei told International Business Times in an interview recently, its ambition for the next five years is simply survival. "In the coming three to five years it is as much about survival as it is about growth. If we can grow at a healthy pace -- not too fast, not too slow -- while we survive, I think that's a great goal for the next few years."

OnePlus is seen as an independent smartphone company founded by two former employees of the Chinese smartphone company Oppo. However the company is wholly owned by Oppo and is a sub-brand of the company set up to appeal to a different customer base in other parts of the world.